皖南山区一次暴雪过程地转适应锋生条件分析  

Analysis of geostrophic adjustment to frontogenesis conditions during a heavy snowstorm in the mountainous area of southern Anhui Province

作　　者：刘裕禄 岳如画 姚叶青[2] LIU Yulu;YUE Ruhua;YAO Yeqing(Huangshan City Observatory of Anhui Province,Huangshan 245021;Public Meteorological Service Center of Anhui Provincial Meteorological Bureau,Hefei 230031)

机构地区：[1]安徽省黄山市气象台,黄山245021 [2]安徽省气象局公共气象服务中心,合肥230031

出　　处：《暴雨灾害》2024年第1期23-31,共9页Torrential Rain and Disasters

基　　金：安徽省气象局创新发展专项(CXM202207);安徽省气象局复盘总结专项(KY202310)。

摘　　要：地转适应是形成皖南山区地形静止锋且区别平衡锋的另一种锋生机制,而地形静止锋常造成皖南山区局地灾害性天气。因此,开展地转适应锋生条件分析研究对于认识山地地形如何造成灾害性天气有重要意义。以2022年2月22日地形静止锋导致皖南山区暴雪过程为例,利用地面气象观测资料、新一代多普勒天气雷达(CINRAD/SA)基数据资料及欧洲中期天气预报中心ERA5再分析资料,采用雷达三维风场反演技术,计算此次暴雪过程的锋生函数。结果表明:(1)此次锋生过程,东北气流入流增强,流函数梯度增大,造成皖南山区背风坡山脚(30.5°—31.0°N)之间流体密度不连续,在其前沿狭窄区内出现地转适应锋生,随即出现了尺度小、呈纬向分布的局地暴雪天气;地转适应锋生和暴雪天气均发生在中低层为稳定大气层结的湿对称不稳定区内。(2)分析锋生函数及相关因子可见,垂直运动倾斜项对地面锋生贡献占主导作用,水平变形项和辐合项锋生贡献相对很小,说明此次地转适应锋生主要是地面上升运动位温垂直输送作用的结果,非风场形变引起。(3)雷达反演的中尺度风场可见,在风场非平衡状态向地转平衡状态调整的过程中,地形强迫下坡风抬升激发锋区上空1.5~3.0 km高度上的大气中低层出现很强的次级环流,导致在地面冷区冷平流增强降温,地面暖区上空因暴雪降水凝结潜热释放的非绝热加热导致增温,使得锋区位温梯度增大,出现锋生现象。Geostrophic adaptation is another frontogenesis mechanism that forms a stationary front,which differs from the balanced front,but often leads to local catastrophic weather in the mountainous area of southern Anhui.Conducting analysis and research on the frontogenesis conditions of geostrophic adaptation is of great significance for how mountainous terrain causes catastrophic weather.Taking the formation of a stationary front on 22 February 2022,which resulted in a local blizzard as an example,the quasi-geostrophic frontogenesis function of topo-graphic frontogenesis is calculated and analyzed based on the following dataset,including the high-resolution hourly reanalysis data from the European meteorological center ERA and conventional data from ground stations,the new generation Doppler(CINRAD/SA)weather radar data,the 3-D wind field data obtained with a 3-D wind field inversion technique and the interpolation method with the accuracy of 0.02°×0.02°.The results are as follows.(1)During this frontogenesis process,the northeast wind flow on the ground intensified,and the gradient of the flow function increased,resulting in discontinuous fluid density at the foot of the leeward slope(30.5°—31.0°N),which leads to geo-strophic adjustment to frontogenesis in a narrow area at its front.Thus,a local snowstorm with a small scale and short duration occurred.The geostrophic adjustment to frontogenesis occurs in a stable atmospheric structure and an environment of wet symmetry instability.(2)By ana-lyzing the four terms of the surface frontogenesis function and their related factors,it is shown that the contribution of vertical motion tilt term to frontogenesis is dominant,while the horizontal deformation and convergence have minor contributions.It indicates that the geostrophic ad-justment to frontogenesis is mainly the result of the upward transportation of potential temperature,rather than the deformation of the wind field.(3)By analyzing the four terms of the high-altitude frontogenesis function and the mesoscale

关 键 词：地转适应锋生 锋生函数 地形 次级环流 

分 类 号：P441[天文地球—大气科学及气象学]